Rebecca Kosloff, MD Is Co-Author on a Case Study of Exceptional Response to Pembrolizumab in Patient with Castration-Resistant Prostate Cancer

Fort Myers, FL – July 1, 2019… Florida Cancer Specialists & Research Institute (FCS) physician Dr. Rebecca Kosloff, who practices in the Bonita Springs and Naples West offices of FCS, co-authored a case study of a male patient with Castration-Resistant Prostate Cancer (CRPC), with pancytopenia (a deficiency of all three cellular components of the blood: red cells, white cells and platelets) caused by myelophthisis (displacement of bone marrow tissue by tumors, fibrosis or granulomas). The case study, titled “Exceptional Response to Pembrolizumab in a Patient with Castration-Resistant Prostate Cancer with Pancytopenia from Myelophthisis,” was published April 9, 2019 online in the Journal of Oncology Practice, followed by print publication June 1, 2019. 

Headshot-for-Press-Release-Rebecca-Kosloff-MD-1As stated in the article, “Myelophthisis is a clinical problem in men with prostate cancer, and the development of pancytopenia due to bone marrow infiltration by therapy-resistant tumor remains one of the most difficult problems to treat.” The patient in the study initially presented in 1999 and underwent a prostatectomy followed by radiation; however, he had recurrence nine years later. He continued to have further disease progression, including metastasis to the bone and bone marrow.

Pembrolizumab, an immunotherapy drug, was administered to treat the patient’s progressive metastatic CRPC with pancytopenia, due to his mismatch repair (MMR) deficiency, a type of gene mutation. The results were almost immediate, according to the study: “Blood counts and PSA measurements showed marked improvement upon treatment initiation …  His favorable outcome is ongoing, most recently documented on scans from August 2018…”  Scans showed no active bone metastases; the patient’s PSA was “undetectable” and “his blood count has recovered.”

Dr. Kosloff and her co-authors concluded, “This is the first report to our knowledge of rapid and durable response in an otherwise unmeasureable site of metastatic CRPC disease… personalized therapy of advanced prostate cancer with pembrolizumab in the context of MMR deficiency can be effective in the bone marrow.  This therapy should be considered by clinicians for treatment of myelophthisis.”


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Recognized by the American Society of Clinical Oncology (ASCO) with a national Clinical Trials Participation Award, Florida Cancer Specialists & Research Institute (FCS) offers patients access to more clinical trials than any private oncology practice in Florida. In the past 4 years, the majority of new cancer drugs approved for use in the U.S. were studied in clinical trials with Florida Cancer Specialists participation.* Trained in such prestigious medical schools and research institutes as Duke, Stanford, Harvard, Emory, M.D. Anderson, and Memorial Sloan Kettering, our physicians are consistently ranked nationally as Top Doctors by U.S. News & World Report.

Founded in 1984, FCS is one of the largest medical oncology/hematology practices in the United States. With more than 230 physicians, 220 advanced practice registered nurses (APRN) and physician assistants (PA) and nearly 100 locations in our network, we are committed to providing world-class cancer care in community-based settings, close to home.

Florida Cancer Specialists has built a national reputation for excellence that is reflected in exceptional and compassionate patient care, driven by innovative clinical research, cutting-edge technologies and advanced treatments, including targeted therapies, genomic-based treatment, and immunotherapy.  Our highest values are embodied by our outstanding team of highly-trained and dedicated physicians, clinicians and staff.

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